Corp Comm Connects

Protecting aquatic habitat critical on York Region sewer project

When a sewer project takes construction crews alongside sensitive waterways, environmental monitoring is critical.
June 26, 2015
By Peter Kenter

For Groundwater Environmental Management Services (GEMS), fulfilling contract requirements on the Regional Municipality of York's Queensville-Holland Landing-Sharon (QHLS) sanitary and water servicing project has involved everything from maintaining the habitat of the endangered redside dace to rescuing distressed snapping turtles displaced by a flood.

The multi-phase QHLS sewer system expansion project is designed to support growth in Holland Landing, Queensville and Sharon in East Gwillimbury and represents part of York Region's Long Term Wastewater Master Plan.

GEMS is the on-site environmental monitor on the construction of the 2.4-kilometre Sharon Trunk sanitary sewer, performing erosion and sediment control monitoring. The construction contract was awarded to Con-Drain and project engineer is MMM Group. The project features installation of a 900-mm line employing a combination of open-cut and trenchless technologies as it passes from hydro right-of-ways through environmentally sensitive zones, such as the Rogers Reservoir Conservation Area.

"We regularly walk the three-kilometre site and inspect erosion and sediment controls to make sure that there are no impacts to Sharon Creek and the Rogers Reservoir wetland," says Ross Mabee, an aquatic biologist with GEMS.

Of particular concern is protection of the habitat of the colourful redside dace, a tiny fish that Mabee refers to as "the rarest fish that's everywhere in the GTA."

"It's endangered in Ontario and theoretically it could live in many areas of the GTA if the habitat supported it," he says. "It's rare enough at this point that I've never seen one in the wild."

During one micro-tunneling exercise under the Sharon Creek, GEMS personnel discovered the signs of a fracture that had occurred in the creek bed.

"It was observable as a sediment upwelling adjacent to the creek and we quickly informed the contractor and the engineer" says Mabee.

On the Holland Landing pumping station upgrade portion of the project, GEMS was contracted to monitor the provincial Permit to Take Water for a one-and-a-half year period concluding in February 2015.

"There was an existing pumping station on the East Holland River flood plain," says Mabee.

"It made more logistical sense to build a new one on that site and eventually decommission the existing one than upgrading. The project included construction of a larger shaft and the driving of caissons into the flood plain."

GEMS activities included daily monitoring of groundwater levels, discharge water quality, surface water quality and groundwater quality in four monitoring wells as many as 400 feet away.

All water removed from the new shaft during construction was placed in a settling tank and then gravity fed through a filter bag placed in the construction area to disperse across the flood plain.

"When concrete work was being completed, we noticed an increase in calcium precipitate in the shaft water near the filter bag," says Mabee. "We periodically cleaned the area with a vacuum truck until we could positively identify the substance and received a permit to discharge it into the existing sanitary sewer."

Mabee notes that stretches of the East Holland River have been channelized in the past to accommodate barge traffic. One of the conditions of construction was to create a backwater aquatic area to improve habitat and facilitate spawning for northern pike.

Once construction was completed and aquatic vegetation planted, two channels would be created, reattaching the refuge to the river. However, in May 2013 prior to the channels being established, aquatic wildlife was stranded in the pond by a flood, culminating in an unscheduled mass rescue operation.

"That wasn't part of the original project," says Mabee. "We had to use a 30-metre seine to net and rescue close to 1,500 aquatic residents. That included a large number of carp, some as large as 20 lbs., two snapping turtles - and one pike."